The present embodiments relate to a gantry for beam guidance of a particle beam.
Particle therapy is a method for the treatment of tissue, such as tumor diseases. Irradiation methods are, however, used in non-therapeutic areas. Non-therapeutic areas include, for example, research as part of particle therapy, which is carried out on non-living models or bodies, or irradiation of materials. Charged particles are accelerated to high energy and are formed into a particle beam and guided to one or more radiation rooms by means of a high-energy beam transport system. In the radiation room, the object to be irradiated is irradiated by the particle beam. “Fixed beam” radiation rooms direct the particle beam to an object to be irradiated from one or more fixed directions. Furthermore, gantry-based radiation rooms direct a particle beam from various variable angular positions via a rotatable beam outlet onto an object to be irradiated. For example, the angular positions may be in a range from more than 180° or 360°.
Because the particles of the particle beam have high energies and the charged particle beam has a high magnetic rigidity, a gantry frequently has heavy dipole magnets to guide the particle beam. The particles may be accelerated protons or carbon ions. The weight of a dipole magnet can, for example, be in the order of approximately 25 t. The components of the gantry, when the gantry is rotated, may come to rest in various angular positions relative to the direction of the force of gravity. The deviation of the components of a gantry from a required set position, however, causes a shift in the particle beam relative to an isocenter and compromises the accuracy of the beam.
In order to be able to enable a spatially precise rotation of the gantry, rigid mechanical parts of the gantry superstructure are known. Where there are cantilevered supporting devices of a gantry, additional supports are often used in the form of bearings in the area of the cantilevered part of the gantry, for example, in the area of the radiation room.
Before commissioning or servicing a gantry, measurements are taken during which the deviation of the particle beam from a desired pattern in the treatment room is measured relative to each angle of rotation of the gantry. Accordingly, in a succeeding act, the spatial pattern may be corrected by a control unit of the particle beam guidance.
The gantry may be rotated to a specific angular position before bringing the gantry into service. The gantry may be rotated to measure the position of the components. Based on the position of the components, the mounting elements for the components, such as the dipoles, may be corrected. This process is carried out iteratively for several angular positions until the mounting elements are adjusted so that the measured deviation from a set position is equally small for all angular positions.